Slash the odds of unluckier attack (4)
I believe the answer is:
nuke
'attack' is the definition.
(as a verb)
'slash the odds of unluckier' is the wordplay.
'slash the odds of' indicates alternate letters (remove the odd letters from).
The alternate letters of 'unluckier' are 'NUKE'.
(Other definitions for nuke that I've seen before include "Attack with H-bomb (slang abbr.)" , "Destroy with a very powerful 18" , "Nuclear weapon (sl.)" , "Drop huge bomb on" , "Attack with an atomic weapon" .)